The role of learning in food intake regulation during early childhood will be investigated. As omnivores, humans learn to eat; individual differences in experiential history are related to differences in food intake regulation, energy balance, and obesity. Research indicates that for adults aversions, preferences, and appetite and satiety can be conditioned through the association of food flavor cues to the physiological consequences of eating. This learning provides a mechanism for anticipating the nutrient consequences of familiar foods and regulating intake accordingly. Such a mechanism is necessary because eating stops before much absorption, thought to produce satiety signals, can occur. During early childhood children are taking an increasingly active role in regulating their food intake, and a great deal of learning about food and eating is occurring as children are introduced to the adult diet of their culture. However, we have almost no data on the role of associative conditioning in the development of food intake regulation in humans. Children's performance in standard associative conditioning paradigms will be investigated. Preschoolers will participate in these experiments, which involve training and test phases (parents are included in the first two experiments as a comparison group). Subjects eat foods with distinct flavor cues that are consistently paired with distinctly different caloric densities. Following repeated exposure to these food cue-caloric density pairings, test trials are given in which the flavor cues previously paired with high and low caloric density loads are presented in foods with identical intermediate caloric density. Consumption and pre- and post-consumption preference measures are taken. These measures indicate subjects' responsiveness to differences in caloric density during training and during testing and the extent to which the flavor cues have acquired control of appetite and satiety, and provide evidence for conditioned preferences. Five experiments are proposed. Experiment I investigates children's unlearned responsiveness to differences in caloric density and "sensory specific satiety." Experiment II is the first conditioning study. Experiment III explores which of the flavor cues available serves as the conditioned stimulus. Experiment IV relates extinction to amount of conditioning and food familiarity. Experiment V explores the relationship between child feeding practices and conditioning by manipulating the social context in which conditioning occurs.